ERR: Improve error message for deprecated frequency aliases in to_offset

[Aniketsy]

#62259.

This PR improves the error message shown when a user specifies a previously-deprecated frequency alias (such as "H", "T", or "S") .

Now, if a deprecated alias is used, the error message clearly states that the alias was removed and suggests the correct replacement (e.g., "Invalid frequency 'H'. This alias was deprecated and removed. Did you mean 'h'?").

Please let me know if my approach or fix needs any improvements . I’m open to feedback and happy to make changes based on suggestions.
Thankyou !

[Aniketsy]

@jorisvandenbossche Could you please review it when you get time?
Thanks!

[Aniketsy]

Hi, @jbrockmendel
To ensure the improved error message for deprecated frequency aliases is applied consistently, all code paths should use the to_offset wrapper from pandas.tseries.frequencies. This requires updating imports of to_offset across the codebase.

from pandas._libs.tslibs.offsets import to_offset
to:
from pandas.tseries.frequencies import to_offset

Is this correct, or would you recommend a different solution?
Thank you!

[jbrockmendel]

This requires updating imports of to_offset across the codebase.

Why? they're the same function. There is no wrapper.

[Aniketsy]

I may have misunderstood earlier, my intention was to ensure that the improved error message for deprecated frequency aliases is displayed consistently. I thought that adding a to_offset wrapper in pandas.tseries.frequencies would help achieve this.

[mroeschke]

Thanks for the PR, but the linked issue appears to have been addressed so closing